Method of manufacturing diamond cutting tools through instantaneous heating process and cooling process and such a diamond cutting tool

ABSTRACT

The present method involves heating a blank, a shank and a welding material in an instantaneous heating process wherein a temperature instantaneously rises at a rate of 500-1000° C./min.; and cooling the blank and the shank at a temperature of 700-1200° C. for a short period of time thus integrating the blank and shank into a cutting tool. The instantaneous heating process is preferably a light heating process by a halogen lamp. A welding chamber for the blank controls both pressure and atmosphere, and is provided with a desired degree of vacuum. In this manner, a thermal deterioration of a diamond blank, a welding metal or a shank material is prevented.

TECHNICAL FIELD

The present invention relates, in general, to a method of manufacturingdiamond cutting tools through an instantaneous heating process and aquick cooling process and to a diamond cutting tool manufactured by themethod and, more particularly, to a method of manufacturing diamondcutting tools by integrating a shank and a blank together into a desiredcutting tool or a desired abrasion resistant tool through aninstantaneous heating process and a cooling process, with the blankbeing made of natural diamond, polycrystalline diamond (PCD), chemicalvapor deposited (CVD) thick or thin diamond, or a cubic boron nitride(CBN), the present invention also relating to a diamond cutting toolproduced through such a method.

BACKGROUND ART

As well known to those skilled in the art, diamond and cubic boronnitrides are optimum materials of putting tools since they have a highabrasion resistance and high machining properties.

A variety of materials, such as natural diamond, polycrystalline diamond(PCD) sintered with metal, chemical vapor deposited (CVD) thick diamondproduced through a vapor deposition process, and polycrystalline cubicboron nitrides (PCBN), have been proposed and used as materials of suchdiamond cutting tools.

The above-mentioned materials for the diamond cutting tools have beentypically prepared in the form of sheet blanks. That is, when a desireddiamond cutting tool or a desired diamond dresser (hereinbelow, referredto simply as “diamond cutting tool” for ease of description) is producedusing such materials, it is necessary to primarily prepare a sheet blank1 made of diamond, PCBN or CVD thick diamond, and to firmly integratethe blank 1 with a shank 3 into a single body using a welding material 2as shown in FIGS. 1 and 2. In such a diamond cutting tool, the weldingmaterial 2 is made of a welding metal alloy, while the shank 3 acts as asupport of the cutting tool and is typically made of a cemented carbide(WC-Co alloy) or a tool steel.

In the above diamond cutting tool, the welding material 2, or theintegration material used for jointing the blank 1 to the shank 3, alsoacts at a medium transmitting the cutting load to the shank 3, with thecutting load being generated between the blank 1 and a workpiece duringa cutting operation of the tool. Therefore, it is necessary for thewelding material 2 to have a high strength enough to effectively resistagainst such cutting load and to retain the integration of the blank 1with the shank 3.

It has been thus noted that the technique of integrating the blank 1with the shank 3 using such a welding material is a very importantfactor while producing such a diamond cutting tool.

In the prior art, such an integration has been accomplished through awelding process using a torch lamp or an induction heater.

However, such a conventional welding process of producing the diamondcutting tools has to be performed under the condition that the weldingmaterial is heated at a high temperature and is exposed to atmosphericair. The welding process thus undesirably oxidizes the welding layer,formed in a resulting tool by the welding material, and forms aplurality of pores in the structure of the welding layer. This finallyreduces the physical properties of the resulting cutting tools. Anotherproblem, derived in the conventional welding process, resides in thatthe process has to be performed manually and undesirably reducesproductivity while producing such tools. The conventional weldingprocess also allows the physical properties of resulting tools to bedifferent from each other in accordance with producers of the tools. Itis thus almost impossible for the welding process to produce diamondcutting tools having equal properties.

In an effort to overcome the above-mentioned problems, another weldingprocess using a vacuum furnace has been proposed.

However, the welding process using such a vacuum furnace consumes alengthy period of time, at least 8-10 hours, while raising and loweringthe temperature to desired degrees. The above process thus undesirablyrequires a lengthy period of processing time while producing the cuttingtools. During this welding process, the shank is undesirably heated at awelding temperature, and so the shank is reduced in mechanical strength.Therefore, the resulting tools of the above welding process areregrettably limited in use.

The above-mentioned problems of the conventional processes finallyresult in an increase in the production cost of diamond cutting tools.

It is thus necessary to provide a new welding process of producingdiamond cutting tools, which reduces the processing cost, producesdiamond cutting tools having equal properties, and allows such cuttingtools to be automatically produced in commercial quantity, thus almostcompletely overcoming the problems derived in the conventionalprocesses.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a method of manufacturing diamond cutting toolsby heating both a diamond sheet blank and a welding material through aninstantaneous heating process without heating a shank whileappropriately controlling a welding atmosphere, thus integrating theblank with the shank into a desired diamond cutting tool and quicklyproducing a desired number of tools having equal properties.

In order to accomplish the above-mentioned object, the present inventionuses a light heating process, using a halogen lamp, as the instantaneousheating process while producing diamond cutting tools. In the method ofthis invention, a welding chamber for blanks is designed to becontrolled in both pressure and atmosphere so as to accomplish a desireddegree of vacuum ranging from almost zero up to several ten Torr, thusaccomplishing a desired atmosphere capable of preventing a thermaldeterioration of a diamond blank, a welding metal or a shank material.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an exploded perspective view, showing a diamond or PCBN blank,a welding material and a shank of a cutting tool before they are weldedtogether in a single structure;

FIG. 2 is a vertical cross-sectioned view of the cutting tool of FIG. 1after the parts are welded together into a desired tool

FIG. 3 is a schematic view, showing the construction of a weldingmachine used in the method according to the preferred embodiment of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 3 schematically shows the construction of a welding machine,designed to weld a blank to a shank through an instantaneous heatingprocess and a quick cooling process in the method of this invention.

As shown in the drawing, the welding machine comprises a heat sourceunit 4 having a plurality of heat sources 5. A welding chamber 6 isprovided in the welding machine and is used for receiving tool pieces 10to be welded therein. An atmosphere controller 8, such as a vacuum pump,is connected to the chamber 6 and controls the inner pressure of thechamber 6 so as to accomplish a desired degree of vacuum of the chamber6.

In the above welding machine, the heat sources 5 of the unit 4 are lightheating type heat sources and accomplish an instantaneous heatingprocess wherein the heating temperature rises to a desired pointinstantaneously. In the present invention, it is preferable to use ahalogen lamp as each heat source 5.

The welding machine of this invention is preferably coated with metal soas to effectively concentrate radiant heat from the halogen lamps 5 tothe tool pieces 10 within the chamber 6.

In the present invention, the number of and the size of halogen lampsare preferably determined in accordance with the sizes of both the toolpieces 10 and the chamber 6.

Both the heat source unit 4 and the chamber 6 are designed to bewater-cooled, with separate hydro-cooling structures 9 respectivelyconnected to the unit 4 and the chamber 6. Due to the hydro-coolingstructures 9, it is possible to prevent both the unit 4 and the chamber6 from being unexpectedly overheated and to allow a quick lowering oftemperature in the case of turning off the heat source unit 4.

That is, the heat source unit 4 is designed to be a separate unitindependent from the welding chamber 6, and so the unit 4 is turned off.Therefore, it is possible to maximize the cooling rate of the weldingmachine.

A transparent silica window 7 forms a wall of the chamber 6, at whichthe chamber 6 faces the heat source unit 4. The above window 7 thusdirectly transmits radiant heat from the halogen lamps 5 to the toolpieces 10 within the welding chamber 6.

Within the chamber 6, the radiant heat, directly transmitted from thehalogen lamps to the tool pieces 10 through the window 7, is veryquickly transferred to a welding material 2 due to a high thermalconductivity of diamond, thus accomplishing a very effective weldingoperation. In such a case, the welding material 2 is made of a weldingmetal and is positioned under a diamond blank.

In such a welding process, it is possible for the atmosphere controller8, such as a vacuum pump, to control the pressure and atmosphere of thechamber 6 so as to give a desired degree of vacuum ranging from 0.001Torr to 20 Torr to the chamber 6.

Therefore, it is noted that the welding machine of this invention has asimple construction and is easily controlled during an operation.

The method of this invention, wherein a thin diamond blank is welded toa shank into a desired diamond cutting tool using the above-mentionedwelding machine, is processed as follows.

First, a thick diamond film, manufactured through a vapor depositionprocess, is laid on a welding metal layer coated on a shank prior to bedried within a drier at a temperature of 200° C. for 10 minutes. A toolpiece 10 is thus prepared.

After the drying step, the tool piece 10 is received in the chamber 6,and the atmosphere controller 8 is started to give a degree of vacuumranging from 0.001 Torr to 0.01 Torr within the chamber 6.

The heat sources, or the halogen lamps 5 are, thereafter, turned on soas to heat the chamber 6 at a temperature of 250° C. for 10 minutes.This step removes impurities, such as organic impurities, from thewelding metal 2 of the tool piece 10.

Thereafter, the temperature of the chamber 6 is instantaneously raisedto 800° C. within 1 minute, and the chamber 6 is kept at the temperatureof 800° C. for 3 minutes. After the chamber 6 is kept at thattemperature for 3 minutes, the halogen lamps 5 are turned off so as toallow the temperature of the chamber 6 to be lowered to 150° C. withinabout 5-10 minutes.

For example, in order to maintain a desired reducing atmosphere withinthe chamber 6, hydrogen having a high purity (at least 99.99%) passesthrough sulfuric acid prior to flowing within the chamber 6. Inaddition, it is necessary to maintain a degree of vacuum of 2 Torrwithin the chamber 6.

Thereafter, the temperature of the chamber 6 is instantaneously raisedto 800° C. within 1 minute, and the chamber 6 is kept at the temperatureof 800° C. for 3 minutes. After the chamber 6 is kept at thattemperature for 3 minutes, the halogen lamps 5 are turned off in thesame manner as that described above, thus quickly lowering thetemperature of the chamber 6.

Therefore, a diamond blank 1 is completely integrated with the shank 3into a single structure.

The above-mentioned process of this invention effectively uses thethermal properties of diamond blanks 1.

That is, diamond has a high thermal conductivity and a low specific heatcapacity in comparison with other materials, and so diamond is veryquickly heated to a desired temperature. The diamond blank thus veryquickly transfers heat to the welding metal 2. In addition, since thesize of the diamond blank 1 is significantly smaller than the shank 3,the blank 1 has a low thermal capacity.

Due to such thermal properties of diamond blanks, it is possible to usesuch an instantaneous heating process in the method of this invention.

In the method of this invention, only the blank 1 and the welding metal2 are heated to a melting point of the welding metal 2 through a lightheating process, thus completely welding the blank 1 to the shank 3.During such a welding process, the shank 3 is not highly heated, but ismaintained at a temperature slightly higher than room temperature due toits high thermal capacity.

Therefore, the tool piece 10 is free from a thermal deterioration, suchas a thermal deformation due to a high temperature, and is quicklyprocessed within a very short period of time during a welding process.

The above-mentioned method of this invention is also effectively usedfor manufacturing cutting tools using PCD (polycrystalline diamond)blanks or PCBN (polycrystalline cubic boron nitride) blanks through aninstantaneous heating processs.

In such a case, the process of manufacturing PCD or PCBN cutting toolsis performed in the same manner as that described for the diamondcutting tool while appropriately controlling the instantaneously raisedtemperature and the heating time in accordance with the size andthickness of the PCD blanks or the PCBN blanks.

In addition, the above-mentioned method of this invention is used formanufacturing diamond cutting tools using natural or synthetic diamond.

In such a case, it is necessary to slowly cool the tool piece for 1-2hours in order to prevent a formation of cracks due to a difference in acoefficient of thermal expansion between diamond and welding metalduring a cooling process.

INDUSTRIAL APPLICABILITY

As described above, the present invention provides a method ofmanufacturing diamond cutting tools. The method of this invention uses awelding machine designed to instantaneously heat both a diamond blankand welding metal at a high temperature for several seconds or severalminutes using a new heat source and to be controlled in a degree ofvacuum ranging from 0.001 Torr to 20 Torr. The method of this inventionthus effectively manufactures diamond cutting tools in commercialquantity by welding diamond blanks or cubic boron nitride (CBN) blanksto cemented carbide shanks, nonferrous shanks or metal shanks.

The method of this invention uses a new heating process capable ofreducing the total processing time to 20-60 minutes, thus manufacturingdiamond cutting tools having a desired integration strength at thewelded junction while almost completely preventing a thermaldeterioration of the resulting tools.

The present invention completely automates the process of integratingblanks with shanks while manufacturing diamond cutting tools or PCBN(polycrystalline cubic boron nitride) cutting tools.

The present invention also provides a method of integratingpolycrystalline diamond with a cemented carbide shank, thus improvingproductivity, operational performance and market competitiveness ofdiamond cutting tools. Another advantage of the method of this inventionresides in that it effectively integrates diamond or PCBN with shanks,made of a variety of materials, thus being widely used for manufacturingdiamond cutting tools.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. In a method of manufacturing a cutting toolcomprising positioning a welding material between a blank and a shankand welding the blank to the shank with the welding materialtherebetween, the improvement comprising: heating the blank, the shankand the welding material through an instantaneous heating process in anarea wherein a temperature instantaneously rises at a rate of 500-1000°C./min.; and cooling the blank, the shank and the welding material byleaving them at a temperature of 700-1200° C. for a short period of timethus integrating the blank with the shank into the cutting tool.
 2. Themethod according to claim 1, wherein the instantaneous heating processis performed using light heat emitted from a halogen lamp used as a heatsource.
 3. The method according to claim 1, wherein radiant heat, havingan instantaneously rising temperature and being emitted from a heatsource, is directly transferred to the blank through a transparentsilica window.
 4. The method according to claim 1, wherein a chamber isprovided for carrying out an integration of the blank with the shank,said chamber having a low vacuum atmosphere with a degree of vacuumranging from 0.001 Torr to 20 Torr.
 5. The method according to claim 1,wherein said blank is a polycrystalline cubic boron nitride blank. 6.The method according to claim 1, wherein the heating is conducted so asto heat the blank and the welding material to a melting point of thewelding material while a temperature of the shank is maintained at atemperature that is lower than said melting point.
 7. The methodaccording to claim 6, wherein the blank comprises a blank materialselected from the group consisting of natural diamond, polycrystallinediamond, and polycrystalline cubic boron nitride.
 8. The methodaccording to claim 7, wherein the blank is a sheet of said blankmaterial.
 9. The method according to claim 7, wherein the shankcomprises a cemented carbide or a tool steel.